大学のコンテストの質問 D PHP は世界で最高の言語です (2 部グラフの色付け + 再帰)

#include<cstdio>  #include<cstring>  #include<cmath>  #include<cstdlib>  #include<iostream>  #include<algorithm>  #include<vector>  #include<map>  #include<queue>  #include<stack> #include<string>#include<map> #include<set>using namespace std;  #define LL long long  const int maxn = 100 + 5;const int INF = 1000000000;int color[maxn];//vector<int> G[maxn];int G[maxn][maxn];int one, two, num[maxn][2], n;int d[maxn][maxn];bool bipartite(int u) {                       //判断节点u所在的联通分量是否为二分图 	if(color[u] == 1) one++;	else two++;	for(int v = 1; v <= n; v++) {		if(G[u][v] && u != v) {			if(color[u] == color[v]) return false;			if(!color[v]) {				color[v] = 3 - color[u];				if(!bipartite(v)) return false; 			}		}	}	return true;} int main() {	freopen("input.txt", "r", stdin);	int t; scanf("%d", &t);	while(t--) {		memset(d, 0, sizeof(d));		memset(color, 0, sizeof(color));		int m; scanf("%d%d", &n, &m);		for(int i = 1; i <= n; i++)			for(int j = 1; j <= n; j++) G[i][j] = 1;		for(int i = 0; i < m; i++) {			int u, v; scanf("%d%d", &u, &v);			if(G[u][v]) G[u][v] = G[v][u] = 0;		}				int cnt = 0, tag = 1;		for(int i = 1; i <=n; i++) {			if(!color[i]) {				one = 0, two = 0;				color[i] = 1;				if(!bipartite(i)) {					tag = 0;					break;				}				num[cnt][0] = one;				num[cnt][1] = two;				cnt++;			} 		}				if(!tag) printf("No solution\n");		else {			for(int i = 0; i < cnt; i++) {				if(i == 0) d[i][num[i][0]] = d[i][num[i][1]] = 1;				else for(int j = 0; j <= n; j++) if(d[i - 1][j]) d[i][j + num[i][0]] = d[i][j + num[i][1]] = 1;			}			int ans = 1;			for(int i = n/2; i; i--) if(d[cnt - 1][i]) {				ans = i;				break;			}			printf("%d\n", ans);		}	}	return 0;}